1. Field of the Invention
The present invention relates to a hue control circuit for use in a color television receiver and, more particularly, to a hue control circuit for reproducing a flesh tone and other colors faithfully.
2. Description of the Prior Art
It is well known that human eyes are most sensitive to a flesh tone and, therefore, when a chrominance signal of a flesh tone, which is distorted in a transmission path or in a color TV receiver, is reproduced through a color TV receiver, a viewer senses a reproduced hue as a unnatural hue as compared with a normal flesh tone even if the distortion is slight.
To avoid such problem, an ACCU-TINT method has been proposed.
This method teaches to reduce the Q component of color signal in a color television system, wherein the Q component is designated by an axis perpendicular to the I axis which coincides near a flesh tone. According to the method, for example, a red which is represented by a vector R shown in FIG. 1 moves to the I axis by reducing the Q component of the R vector the resultant vector can be represented by R'. Therefore, a color signal near the I axis is drawn to the I axis, so that flesh tone can be reproduced faithfully.
However, this ACCU-TINT method has a disadvantage that hue and saturation of colors of magenta Mg, blue B, cyan Cy and green G are unnecessarily distorted as shown by Mg', B', Cy' and G' by decreasing respective Q components of these colors. This distortion of the colors appears strongly on the color near the Q axis so that, particularly, a green becomes bluish whereby a green leaf is reproduced in abnormal tone.
To remove the disadvantage, such system as to inhibit operation of reduction of Q component in response to (G-Y) signal, when a green signal is applied to a color demodulator may be proposed.
However, this system still has a disadvantage that because a switching level for designating whether the Q component should be reduced or not is set on a level represented by a line S as shown in FIG. 2, when a light green of which vector is shown by G' is reproduced, the Q component of the G" is decreased and, consequently, the light green become bluish. On the other hand, when the switching level is set as shown S' in FIG. 3, the Q component of the light green can be maintained as a original value so that the light green can be reproduced in normal color. However, in this case, the range where color compensation for reproducing a normal flesh tone can be performed by decreasing the Q component of a color signal will be narrowed to a value as shown by D in FIG. 3 and, consequently, desirable flesh tone may not be reproduced.